Modern Telemetry Part 14 pptx

The larger lake sturgeon spent a significant amount of time in the water column and at the surface.. The selection of depth based on horizontal and vertical movements of lake sturgeon se

Fig 9 Digital elevation model of Fig 10 Depth availability in Round Lake Round Lake

Fig 11 Hardness map of Pigeon River at Fig 12 Hardness (substrate) availability in

Substrate and Depth: Maximum depth of Round Lake is 16m A depth map of Round Lake is

shown in Fig 9 Two deep holes, one off the Northeast corner of each island, are found in

the lake The general structure is bowl shaped Depth availability is shown in Fig 10 Two and three meters depths are available 33 and 16% respectively Seven, 8, and 9 meter depths are available 5, 6, and 8% respectively

Substrate hardness of the lake is shown in Fig 11 Substrate was generally related to depth The deeper areas of the lake had softer substrates with a high percentage of silt The shallow sections along the shoreline to about 10m depth had sandy substrates Cobble and rock substrate predominated in areas of high flow at the inlet and outlet Availability of substrate hardness was 11, 25, and 17 percent for hardness values of 125 (coarse sand), 130 (gravel),

0 5 10 15 20 25 30 35

Hardness = 150 (Rock) Hardness = 95 (Clay)

0 5

and 135 (medium sand) respectively (Fig 12) Substrate hardness of 110 (fine sand) had a

Table 3 Sediment classification scheme for Round Lake

Thirty–seven sediment grabs were taken to compare with the hardness values obtained

from the sonic data Table 3 lists the substrate classification given to each range of hardness

values Hardness values range from 95 (clay) to 150 (rock, see Fig 11)

4 Lake sturgeon movements

The biological data for the nine lake sturgeon tagged with acoustic tags are listed in Table 2

The nine fish were tracked for 27 days and 15,446 locations were obtained Movements

ranged from individuals that were mostly sedentary to highly mobile individuals Daily

movements were variable between fish as well as by the same fish on different days Figure

13 shows the locations of fish 4015 on four separate days Movement was confined to the

inlet to Round Lake on day 210 Movement increased on days 211 and 212 and covered most

of the lake Movement on day 220 was restricted to the river outlet

A comparison of the movements of juvenile and adult lake sturgeon is shown in Fig 14

Movements of the juvenile fish were focused at the inlet and outlet and in the deep hole

(~16 m) Movements of the subadult and adult lake sturgeon were also associated with

the inlet and outlet but the movements were more widespread around the lake The

channel where water entered the lake was a preferred site as was the outlet from the lake

Figure 15 shows the swimming depth of sturgeon 4014 on day 206 relative to the bottom

depth Note the day 206 is based on January 1 being day 1 Sturgeon 4014 was on the

bottom 30% of all locations on day 206 During the hours from midnight to 5 AM sturgeon

4014 was in the water column the majority of the time From 5 AM to 11 PM more time

was spent on the bottom After 11 PM lakes sturgeon movements shifted to the water

column Figure 16 shows sturgeon 4015 on day 221 where 53% of all locations were on the

bottom on day 221 Sturgeon 4017 on day 211 was on the bottom for the entire day but

periodically swam to the surface (Fig 17) Figure 18 shows the overall distribution of each

lake sturgeon fitted with a pressure tag and the total distribution of all fish on the bottom

and in the water column

Fig 13 Movements of lake sturgeon 4015 on four separate days

Fig 14 Comparison of the movements of adult and juvenile sturgeon in Round Lake

Juvenile Adult Fish

A) Fish 4015, Day 210 C) Fish 4015, Day 212

B) Fish 4015, Day 211 D) Fish 4015 Day 220

Fig 15 A comparison of swimming depth Fig 16 A comparison of swimming depth and

0 10 20 30 40 50 60 70 80 90 100

% in the water column

Fig 17 A comparison of swimming depth Fig 18 Time spent in the water column and on

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

Figure 20 shows substrate selection of sturgeon 4014, 4015, 4017 from the 7 day sample Substrate with a hardness value of 110 was selected 53% of all locations

Overall, lake sturgeons were located on the bottom 39% and in the water column 61% of the locations on the 7 day sample (day 215 based on January 1 being day 1)

The amount of time spent at the surface varied with time of day The majority of locations

< 1m occurred between the hours of 8 PM and 8 AM (Fig 19)

The selection of depth was analysed from two perspectives Figure 21 shows the overall

depth selection of the three lake sturgeon tagged with depth tags Thirty percent of all locations were less than two meters Sixty-six percent were less than four meters Figure 22 shows the depth selection of the three lake sturgeon including only the locations in which they were in contact with the substrate during the 7 day sample Seven, 8, and 9 meter depths were selected 11, 31, and 21 percent respectively Figure 23 shows movements of lake sturgeon 4014 It spent 70% of the time in the water column at the inlet on day 206 and on day 221 lake sturgeon 4014 spent 47% of the time in the water column

Figure 24 shows movements of lake sturgeon 4015 on day 210 It spent 59% of its time in the water column at the inlet of the river Lake sturgeon 4017 (Fig 25) spent 60% of the time in the water column on days 206 and 222, 25% on day 211, and 88% on day 219 On days 211 and 219, sturgeon 4017 covered most of lake, including areas around the inlet and outlet The use of depth tags eliminates the guess work of whether a fish was on the bottom or in the water column at each position Comparisons were made in this study among telemetry position, depth and substrate using data from depth tags Substrate, depth and current were the three primary environmental variables measured

Lake sturgeon movements ranged from sedentary to highly active Movements in the areas

of the inlet and outlet, areas of higher flow rate were quite common as well as movements in the deeper areas and along the natural flow of the river Movements along the shorelines were rare Along the shorelines the water is shallow, there is little flow, and the substrate is primarily sandy Movements of smaller and larger fish were similar but larger fish moved greater distances Nevertheless, juvenile fish appear to use most of the same habitat as the larger fish Movements for both were related to the inlet and outlet and the deeper part of the lake

The larger lake sturgeon spent a significant amount of time in the water column and at the surface We do not know what juveniles were doing concerning depth selection because they were too small to be fitted with tags with pressure sensors The amount of time in the water column by the larger fish suggests these fish were feeding on organisms drifting with the current A majority of the records on movement were near the inlet and outlet where drift nets recovered insects and the occasional small fish Extensive lake sturgeon activity was noted where insects were carried by the current, were floating on the surface, or were emerging i.e mayflies High sturgeon activity in some areas was also correlated with clam beds

The timing of movements in the water column and at the surface was correlated to light intensity Lake sturgeon spent more time at the surface at night than during the day, when more time was spent on the bottom

Based on the comparison of substrate selection and substrate availability lake sturgeon were found over fine sand, cobble, and rock substrate at higher frequencies than the proportion of this substrate in the lake Coarse sand and gravel substrates were selected at a lower frequency than their proportions in the lake

Fig 19 Day and night comparison of time spent at the surface for sturgeon 4014, 4015, and

4017

Fig 20 Substrate selection by lake sturgeon in Round Lake (see Table 3)

Hexagenia (Ephemeridae) is a common prey item of lake sturgeon and silt and clay

substrates are the preferred habitats By contrast clams were often found in sandy substrates While invertebrates were not common in the sieved substrates mayflies are a major food source for most fish species in the lake Similarly, mayflies were a major food item of lake sturgeon, based on stomach contents which was verified by gavage It appears

in this system that mayflies are a major food source but competition for this food source by most fish species in the lake may make this food item a potentially limiting factor Similar observations have been reported by others (Choudhury et al 1995; Chiasson et al 1997) The selection of depth based on horizontal and vertical movements of lake sturgeon seems

to be related to current Lake sturgeon tended to stay in the water column more often in areas of high flow such as the inlet and outlet Since the study took place in mid summer and this activity was not related to spawning behaviours or movement related to fall/winter migrations the majority of movements are likely related to feeding behaviour

0 50 100 150 200 250 300

95 100 105 110 115 120 125 130 135 140 145 Substrate Hardness

Fig 23 Movements and depth Fig 24 Movements and depth selection of lake

Fig 25 Movements and depth selection of lake sturgeon 4017

Unknown Depth

On the bottom

In the water column

23 On the bottomUnknown depth

In the water column

5 Current profiling

Since lake sturgeon movements and substrate were being evaluated in Round Lake and there was evidence that currents had a role in their distribution we evaluated current

distribution in the lake Figure 26A illustrates the cross sections of the river and lake where

data was collected for current profiling and Fig 26B identifies transects for which data was presented and discussed in the text

Current profiling was done with the RDI Workhorse (Acoustic Doppler Current Profiler) This system was initially designed for stationary applications but its use was broadened to include total discharge measurements of streams and rivers and to measure currents in the areas where fish moved This can be done from small moving boats

Fig 26 Transects for the current profile measurements in the Pigeon River at Round Lake A) all transects throughout the lake and B) includes transects where current profiles are presented in this report with additional transects and current profiles also shown tagged lake sturgeon where in these areas for extended periods of time Red dots = location of radio tagged lake sturgeon

Data collection focused in the areas of greatest activity in the Pigeon River in and around Round Lake because lake sturgeon tagged with radio and sonar tags moved short distance upstream to Grant Falls and downstream to the second rapids (Fig 26A)

Current profiles: Current profiles were taken in 1997, 2000, 2001 Movements of lake sturgeon in regions of the Pigeon River above and below Round Lake were determined with radio tags and sites where more transects were run are illustrated in Fig 26A Figure 26B outlines selected cross sections, some of which are discussed below The current cross sections shown in Fig 27 is above the second rapids on the Pigeon River downstream of Round Lake and the graph below the velocity magnitude is the boat or ship track that also

indicates the direction and relative magnitude of the current Note current is measured

across a body of water and in the water column in units referred to as cells The cells are coloured and represent the current in a cell Each cell is coloured in the graph (see velocity

magnitude) and is ~20 cm but cell size may vary depending on depth at the sampling point

The stick ship tract directly below illustrates the ship tract across the river (red) and the blue lines shows relative current flows and direction along the transect The top of the ship tract

is the right side looking downstream, unless otherwise described Figure 27 (transect 1) has

a current ranging from 0.250-1.0 m/sec and while lake sturgeon moved through this area they spent most of their time on the right side in back eddies separated from the main flow

by a ridge on the bottom The current in this area was between 0.25 and 0.750 m/sec In the area of transect 2 (Fig 26B) lake sturgeon moved through this region but did not remain in the area The strongest current encountered throughout this section of the Pigeon River was

up to 2 m/sec The river was shallow about 1.5 m at the narrowest section of the river with turbulence and air bubbles (the reason for the large numbers of blank spaces i e no data)

The current was slightly lower on the left side (looking downstream) and deeper but this was off the main flow Transects 7, 8 and 9 are from a region of the river where considerable

lake sturgeon activity was recorded (Fig 14) It is apparent from the boat track of Fig 28 that

a small back eddy occurs on the right side (looking downstream) From the acoustic tag data there was extensive movement throughout this area indicating that lake sturgeon movements in currents up to 1 m/sec were routine Figure 29 illustrates a transect from a region of Round Lake with high lake sturgeon activity and where currents ranged from 0.00

to 0.250 m/sec Transects 15 (Fig.26B) represents an area of Round Lake where flow from the river entering Round Lake starts to slow Most of the current in the river bed is 0.5 m/sec Figure 30 (transect 16) illustrates the river bottom and shallow area with macrophytes on the right side Macrophytes have a similar affect on the equipment as air bubbles and as result the quality of the data is reduced From the ship track in transect 16

the main flow of the river is becoming apparent and in Fig 30 there is some evidence for a back eddy on the right side This back eddy becomes more pronounced in transect 17 (not shown) but declines in transect 18 (Fig 26B) and the current in both transect 17 and 18 increases to be predominantly 0.7 m/sec Figure 31 (transect 19) illustrates that the strongest current occurs at the point the river enters the lake and the current across the entire river changes its direction as it passes over rocks on the right side The majority of the current in

Fig 31 (transect 19) and transect 20 is between 0.7 and 1.0 m/sec Transect 25 below Grant

Falls has current ranging from 0.7 to 1.0 m/sec This was also a region of the Pigeon River where spawning lake sturgeons were found

Correlation of lake sturgeon movements with current profiles: The overall frequency of movement

of all acoustically tagged lake sturgeon is shown in Fig 14 and it clearly indicates that activity is concentrated at the inlet and outlets to Round Lake In the area of the inlet activity

is concentrated in the main river channel as it enters the lake The current at transect 19 (Fig 26B) is up to 1.0 m/sec but this area is frequented by both large and small sturgeon (Fig 14) It is worth noting that the current close to the contour of the river bed is < 1.0m/sec

so lake sturgeon might be moving through these areas Figure 14 shows that the smallest sturgeon also concentrated much of their activity in the deepest part of the lake and the

main river channel entering the lake (Figs 9 and 14) By contrast the largest sturgeon spent

proportionally less time in the deepest hole in the lake suggesting there may be some segregation of habitat, at the fine scale It was also noteworthy that the smaller lake sturgeon frequented the area to the left of the outlet from Round Lake, again suggesting that there

may be some differences in habitat use between small and large lake sturgeon (Fig 14)

Fig 31 Round Lake ship transect 19 (see 26B)

Interestingly while the larger sturgeon utilized this region they were more offshore The

larger sturgeon were concentrated at the outlet (Fig 14) where currents were 0.25 to

0.5m/sec (Fig 26B, transects 7, 8 and 9) These currents are below those noted for transect 9

at the inlet to Round Lake Clearly there is more to the habitat requirements of juvenile lake sturgeon than a certain level of current It is also apparent that the larger sturgeon frequented areas of the lake where currents were very low (Fig 26B, transect 12) but the ship track suggests a slight amount of counter flow (eddy) in this area However, there was very little activity by smaller sturgeon in this area of the lake The larger acoustically tagged lake sturgeon frequently ventured into the river, upstream and downstream from the lake but did not remain in these areas for extended periods of time as they always returned to the lake None of the tagged lake sturgeon moved out of the area, either due to strong site fidelity or because this region of the Pigeon River is physically isolated due to rapids and small waterfalls

Generally, the smallest lake sturgeon remained in slower flowing water and tended to frequent areas less used by large sturgeon in both deep and shallow regions of the lake Unlike the larger sturgeon the small sturgeons were rarely located in water under 1 meter Larger lake sturgeon can move through water with currents as high as 2m/sec but generally frequent areas with currents less than 1m/sec and if situated in the river tend to locate in the back eddies rather than in the main current Current undoubtedly plays a role in defining lake sturgeon habitat but it is only one of several variables

6 Sturgeon feeding tags

6.1 Background

Lake sturgeon movements in the field are readily identified using different tagging systems but establishing feeding behaviour is somewhat more complicated because one can not observe feeding directly as lake sturgeon generally do not feed at the surface However, results reported in this chapter clearly revealed that lake sturgeon spend a significant proportion of time in the water column and were likely feeding on drift concentrated at the inlet and outlet of the lake, and emerging insects in the lake Consequently a key question was could a sensor be developed to document lake sturgeon feeding? From previous studies

on the histology of larval lake sturgeon we knew that there were extensive pressure receptors inside the mouth of lake sturgeon (Dick, unpubl data) From other observations it was apparent that lake sturgeon utilized the branchial chamber to not only sense and feel the food but also to clean and to expel food with considerable force if the food was found to

be unacceptable (Dick, unpubl data) Furthermore, since lake sturgeons extend their mouth

to feed we hypothesized that this may change the pressure inside the branchial chamber

We also knew that lake sturgeon extended the mouth with and without feeding

Branchial pressure ranges from 50-150 pascals for restrained animals and no studies had attempted to relate branchial pressure to various levels of metabolic activity We expect pressure to be correlated to oxygen consumption but our initial question was to determine if

we could measure differences in the branchial chamber of lake sturgeon Since lake sturgeon feed by sucking in prey and water this action should result in large pressure pulses interrupting rhythmic ventilation pressure pulses It should be possible to distinguish mouth movements associated with feeding, coughing etc The objective was to build a prototype tag to test the feasibility of a pressure tag to monitor branchial chamber pressure and use this as a measure of feeding activity Previous reports by Webber et al (2001a) and Webber et al (2001b) describe the application of pressure tags to measure swimming speeds

The prototype sensor was designed to be attached by wires to the receiver to obtain physiological data The second sensor was designed to transit the signal directly to a receiver The experimental setup for the study is shown in Fig 32

6.3 Results

The original experiments utilized direct wiring from the sensor and the data are represented

by the Analog to Digital conversion (A/D) of the A/D board in the PC (Fig 33)

cannula visible

Fig 34 Flushing cannula with syringe to remove air bubbles

Note occasional negative values